If you are refering to the 420, they are located at the ends of the fuel lines from the Fuel Distributor. You will need to remove the black rubber hoses that connects to each Fuel Injector "holder".
Detach the each fuel line at both ends.
Remove the long rubber air hose attached to each FI holder.
The black plastic holder with the brass injector simply pulls straight out. UP.
Make sure the rubber O-Ring is removed from the intake hole.
Pop the injector out of the holder. You will see the injector "seal" that holds the brass injector in the plastic holder.
You will want to replace the seals, holders, and O-Rings. The O-Rings usually come with the new holders.
Don't be surprised if the holders crumble during removal. They get very brittle with age, heat, just like the rubber bits.
When reinstalling, clean out the holes in the manifold with a rag soaked with carb cleaner.
Grease the manifold holes and new O-Rings with a liberal amount of O-Ring lube.

Dave